1. Field of the Invention
The present invention relates to an automatic balance adjusting centrifuge and the control method thereof, and particularly to an automatic balance adjusting centrifuge calculating the magnitude and the location of the imbalance of the centrifuge by the vibration generated in the dynamic state and automatically compensating for the imbalance based on the calculation result.
2. Description of the Related Art
As is well known, a centrifuge is an essential equipment which is widely used over medical and physiochemical fields, and is an instrument which separates sample elements by rotating a rotor equipped with buckets containing samples at a high speed to provide the samples with high centrifugal acceleration. Thus, high density elements in the samples are placed at the outer layer along the radial direction of the rotor and low density elements in the samples are placed at the inner layer along the radial direction.
In the operation of the centrifuge, imbalance of the centrifugal force is inevitably created by the weight differences among buckets due to the discrepancy in the number of samples within each bucket or in the total weight. However, the conventional centrifuge without the automatic balancing function brought about a problem of imposing the laborious works on users, such as measuring the weight of each sample manually to load the samples with an identical weight on a rotor symmetrically.
To address this problem, the applicant has already suggested several automatic balance type centrifuges and reserved the rights in Korea as patents. To be concrete, Korean patent registration number KR 10-0343336 B1 (registered date: 4 Jun. 2002) (hereafter, it is referred as Preceding Invention 1; PI1) discloses a automatic balance type centrifuge which includes a two-arm type rotor lever and removes the imbalance of weight by transferring a rotor lever in the control of a rotor lever transfer mechanism comprising a worm and a worm wheel after detecting the weight imbalance in both ends of the rotor lever with the help of strain gauges stuck on the maximum bending stress points in both ends of the rotor lever hooking buckets loading samples.
In the next, U.S. Pat. No. 6,949,063 B2 (registered date: 27 Sep. 2005) and U.S. Pat. No. 7,297,097 B2 (registered date: 20 Nov. 2007) (hereafter, it is referred as Preceding Invention 2; PI2) discloses a revised version of the automatic balance type centrifuge of PI1, adopting a fixed type two-arm rotor lever of which the center a movable balance weight is employed at. The centrifuge removes the imbalance of weight by transferring a balance weight in the control of a balance weight transfer mechanism comprising a worm and a worm wheel after detecting the weight imbalance in both ends of the rotor lever with the help of pressure sensors installed beneath both ends of the rotor lever hooking buckets loading samples.
Next, Korean patent registration number KR 10-0615630 B1 (registered date: 17 Aug. 2006) (hereafter, it is referred to Preceding Invention 3; PI3) discloses an automatic balance type centrifuge including a rotor, wherein the rotor comprises: a plurality of rotating arms, e.g. three rotating arms, which support buckets containing samples, have the same radial length from a rotational shaft for centrifuging, and are disposed around the rotational shaft with equal angles; a balance weight installed to be movable along the radial direction of each rotating arm so as to compensate for the imbalance induced by the centrifugal force during centrifugal separation process; and a balance weight transfer mechanism transferring each balance weight horizontally along the radial direction of each corresponding rotating arm. In PI3, detection of imbalance of the centrifugal force, that is, imbalance of bucket weights, for example, can be carried out by an electronic scale which is installed in separate from the rotor and goes up and down in the lower part of each bucket.
Lastly, Korean patent registration number 10-0756231 B1 (registered date: 31 Aug. 2007) (hereafter, it is referred to Preceding Invention 4; PI4) discloses an automatic balance type centrifuge, wherein the imbalance of weight is compensated for by moving a rotor lever itself in the horizontally as in PI1, while the precision of driving the rotor lever is further improved. The detection of imbalance in the weight of buckets, for example, is carried out by an electronic scale which is installed in separate from the rotor and goes up and down in the lower part of each bucket.
However, in the above conventional automatic balance type centrifuges, the imbalance of weight is detected while the rotor is stopped, namely in static state, so that not only configuration of a complex circuit and mechanism is required but also long time is consumed to sense the weight imbalance.
Most of all, there has been a problem that compensation for the imbalance is not performed properly because the imbalance amount of bucket weights and the transfer amount of a balance weight or a rotor lever to correct the imbalance amount are calculated by force from the empirical data or formula obtained from numerous iteration of experiments and the above conventional centrifuges do not take into account the errors in the data or in the formula for calculating, the deviations between the products created during production process, and the change of center of gravity due to mechanical deformation by usage for a long time at all.